1. Field of the Invention
The present invention relates to a data communications apparatus which performs data communications through the telephone line and that is connected to an external information processor such as a personal computer for the external information processor to perform communications through the data communications apparatus, and more specifically, to a facsimile apparatus provided with a facsimile modem function.
2. Description of the Prior Art
A function to directly facsimile-transmit an original such as a document and a drawing made on a personal computer and to receive image data facsimile-transmitted over the telephone line to directly input them to the personal computer is called a PC-FAX function. The PC-FAX function is realized by connecting a personal computer to a facsimile apparatus having a data communications port such as an RS-232C port to use the facsimile apparatus as a facsimile modem.
In connecting a personal computer to a facsimile apparatus, an expansion board provided with an internal register is connected to, for example, an RS-232C port of the facsimile apparatus. The personal computer is connected to the facsimile apparatus through the expansion board, and the expanded function is allotted to a key of an operation unit of the facsimile apparatus.
By attaching the expansion board, various expanded functions are performed such as a function for the personal computer to transmit data via the facsimile apparatus, a function for the personal computer to receive data via the facsimile apparatus, a printing function to use the facsimile apparatus as a printer of the personal computer, and a scanner function to use the facsimile apparatus as a scanner for inputting images to the personal computer. Thus, a recording unit and an original reading unit of the facsimile apparatus can be used also as a printer and a scanner which are necessarily prepared on the side of the personal computer originally, so that it is unnecessary to prepare the expensive peripheral devices, which is very advantageous.
A facsimile apparatus connected to a personal computer operates in two modes: a normal mode (facsimile mode) in which the facsimile apparatus operates alone without performing any data communications with the personal computer; and a PC-FAX mode (facsimile modem mode) in which the facsimile apparatus performs data communications with the personal computer. The changeover between these two modes is made through control from the personal computer by using control commands called AT commands. This changeover is also made manually by operating an operation key provided on the facsimile apparatus.
The reception according to the PC-FAX mode is performed in the following manner: First, the facsimile apparatus set in the PC-FAX mode notifies the personal computer that a call comes in via the outside line. In response to the notification from the facsimile apparatus, the personal computer supplies the facsimile apparatus with an AT command to instruct the facsimile apparatus to receive the call. Receiving the AT command, the facsimile apparatus connects the line and receives the data via the outside line to transmit it to the personal computer.
In a facsimile apparatus operating in the normal mode and in the PC-FAX mode, calls coming in via the outside line cannot be received when the facsimile apparatus is in the PC-FAX mode and the personal computer is supplied with no power. Such a situation occurs, for example, when the user turns off the personal computer after finishing his or her work and when the user forgets to change the operation mode so that the facsimile apparatus is left in the PC-FAX mode. When the user is not at the facsimile apparatus such as in the nighttime, the operation mode cannot be changed to the normal mode when a call comes in, so that the call cannot be received.
Even if the personal computer is provided with power, the same problem is caused if the applications software of the personal computer for performing the PC-FAX function is not activated. The facsimile apparatus set in the PC-FAX mode tries to notify the personal computer that there is an incoming call, but the personal computer does not respond thereto, so that the call cannot be received. No calls can be received until the user notices that the applications software is not activated.
The telephone line is not used while the scanner function and the printing function are executed in the PC-FAX mode. Therefore, a call may come in while these functions are being executed. Conventionally, in such a situation, since data transfer cannot be performed between the facsimile apparatus and the personal computer, reception error occurs although the call is received. Typically, the facsimile apparatus on the transmitting side automatically performs re-dialing when the facsimile apparatus on the receiving side does not receive the call, and provides an error display without performing re-dialing when reception error occurs on the receiving side. The user of the facsimile machine on the transmitting side who is notified of the reception error necessarily performs the transmitting operation again. Since the telephone line is used even when reception error occurs, the user on the transmitting side is charged for the calling.
Further, in the conventional arrangement, if an AT command is transmitted from the personal computer so that the operation mode of the facsimile apparatus is automatically changed to the PC-FAX mode while the facsimile apparatus is performing communication in the normal mode, transmission according to the normal mode cannot be performed. For example, if an AT command is transmitted just before a key is operated to start transmission after an original to be transmitted is set, the user has to wait until the operation according to the PC-FAX mode is finished even when the transmission of the original is urgent.